Eleven civilians and a police officer have been killed by a suicide car bomber in the Iraqi city of Ramadi.
Iraqi police are frequently targets of the country's insurgents
The blast took place at a police checkpoint in the western city, which is a hotbed of the Sunni insurgency.
Meanwhile Iraq's prime minister vowed to catch the "cowards" who killed 14 policemen on Friday.
And the US military said it had killed several "key" insurgents north of Baghdad whom it blamed for shooting down a number of US helicopters.
The air strikes took place near the town of Taji, north of the Iraqi capital.
"Intelligence reports indicated this network is responsible for threats to coalition aircraft," the military said.
The US military and private contractors have lost eight helicopters in Iraq in about six weeks, killing 28 people, most of them in the area north of Baghdad.
In other developments:
- The US says another air strike near Baghdad kills seven al-Qaeda suspects it blames for a large number of suicide car bombs
- Six Sunni Arab men are killed after receiving death threats for attending reconciliation talks with local Shia in Youssufiyah, south of Baghdad
- Gunmen kidnap Thamer Sultan, a senior adviser to the Iraqi defence ministry in Baghdad
Blind eye charges
Iraqi Prime Minister Nouri Maliki has spoken out after the bodies of 14 policemen were found in the streets of Baquba, north of Baghdad, with their throats slit.
An alliance of militant groups said, after they disappeared on Thursday, they would be killed in retaliation for the alleged rape of a Sunni Arab woman.
Mr Maliki has dismissed the rape allegations.
Sunni politicians have accused the police of perpetrating a series of human rights abuses on their community and of turning a blind eye to attacks on them by Shia militants.
Mr Maliki called the policemen's killers "cowards".
"We promise our people that the blood of these martyrs will not go unavenged," he said.
"We will chase them."
But the BBC's Andrew North in Kabul says that with so many incidents like this, the odds are against them being found.
The Shia-dominated police force is constantly targeted by Sunni insurgents. Last month more than 130 police officers died in attacks.